Photoelectric monitoring device for pluralities of threads

ABSTRACT

In a photoelectric monitoring device for pluralities of threads, such as in warp knitting machines, a laser beam is split into a number of parallel partial beams by means of beam splitting partially transparent mirrors arranged in the optical path of the laser beam at an angle to the beam axis thereof. Each such partial beam is directed transversely across one group of threads, the threads of said group being parallel and arranged in one plane, and impinges on an associated photoelectric detector. Air flow means either in the form of an air outlet pipe or in the form of a pipe surrounding the light path of each partial beam, having a longitudinal slot and connected to a suction source make sure that broken threads are moved through the respective partial beam to cause a pulse signal from the detector.

United States Patent [191 Brose 11 Sept. 18, 1973'- [75] Inventor: Peter Brose,Wolfratshausen,

Germany [73] Assignee: Firma Erwin Sick, An der Allee,

Germany [22] Filed: Mar. 10, 1972 [21] Appl. No.: 233,676

[52] U.S. Cl. 250/219 S, 250/219 WE, 356/199 [51] Int. Cl. G0ln 21/30 [58] Field of Search 250/219 DF, 219 WE, 250/219 S, 221, 222; 331/945 A; 356/199,

2,503,023 4/1950 Berry 250/225 Primary Examiner-Archie R. Borchelt Assistant Examiner-D. C. Nelms Attorney-Robertson & Vandenburgh [57] ABSTRACT In a photoelectric monitoring device for pluralities of threads, such as in warp knitting machines, a laser beam is split into a number of parallel partial beams by means of beam splitting partially transparent mirrors arranged in the optical path of the laser beam at an angle to the beam axis thereof. Each such partial beam is directed transversely across one group of threads, the threads of said group being parallel and arranged in one plane, and impinges on an associated photoelectric detector. Air flow means either in the form of an air outlet pipe or in the form of a pipe surrounding the light path [56] References Cited f h l b h 1 l l t d o eac par 1a earn, avmg a ongi u ma s 0 an UNITED STA'TES PATENTS connected to a suction source make sure that broken 3; s threads are moved through the respective partial beam am er 3,677,307 7/1972 Fiorucci 250/219 s to cause a pulse Slgnal fmm the detector 3,659,950 5/1972 Troll 250/219 S 15 Claims, 6 Drawing Figures I a I b 4n 7 f 1 b I 1.. i l I l 1 121 i 121 I F I l llog} 103:, l0n| I l I I I 1'- I I l l I r I t I 1- I l I :20 i 2? l PATENTEDSEP 1 ems SHEEI 1 [1F 5 SHHII 2 I]? 5 oooooououooooooboco000006 ml 0 O O O 0 G O Q O D O O G O O A O G O O O 0 0 ollboooocooooooooooooooooooo 7 Fig. 2

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PIIOTOELECTRIC MONITORING DEVICE FOR PLURALITIES OF THREADS BACKGROUND AND SUMMARY OF THE INVENTION I one group of threads for thread break and to generate a warning signal upon occurrence of a thread break in anyone of these groups of threads, said warning signal, for example, switching-off the machine.

In accordance with the invention the monitoring beams of light are formed by providing a single light source forming a light beam and by arranging a plurality of beam splitting mirrors one behind the other in the optical path of said light beam and at an angle to the beam axis thereof.

Thus each group of threads are monitored by a respective light beam, said light beam having very small cross sectional dimensions. If a thread breaks, the broken thread is moved through said light beam and generates a dark impulse from a photoelectric detector impinged upon by the light beam. In order to produce beams of sufficiently small cross sectional dimensions to enable the generation of a marked dark impulse by the movement of the thread through the beam, the light source is preferably a laser. By the use of the laser and the arrangement of the beam splitting, partially transparent mirrors, all the light beams of the monitoring of the various groups of threads can be produced by one single laser. t In a preferred embodiment of the invention, a first partially transparent mirror is located in the optical path of a laser light beam and at an angle to the beam axis. The partial beam transmitted by said firstmirror is directed across a first group of threads to a'photoelectric detector as a first monitoring light beam. A plurality of additional partially transparent mirrors is located in the optical path of the partial beam reflected by said first mirror at an angle to the beam axis. The partial beams reflected by said additional partially transparent mirrors are directed across additional groups of threads to respective photoelectric detectors as additional beams for the monitoring of the threads.

The partially transparent mirrors may be arranged in parallel to each other and at an angle of 45 with respectto the beam axis. Thereby a system of parallel monitoring beams of light is obtained.

The partially transparent mirrors may be mounted in a tubular housing having windows in its wall for the light beams. Advantageously, the tubular housing comprises a plurality of tubular housing sections, each housing section having one of said partially transparent mirrors mounted therein, the housing sections being connected by means of threaded sleeves or the like. Thus it will be possible, to optionally produce different numbers of monitoring beams of light, in accordance with the respective requirements, by combining the desired numbers of such tubular housing sections.

In order to eliminate the influence of shocks and machine vibrations on the operation of the photoelectric monitoring device, the detector is. preferably located in the focal point of a detector optical system, the aperture of said detector optical system being large as compared with the beamcross section. A housing containing the laser and the partially transparent mirrors may be supported by vibration damping means, said vibration damping means being designed, however, to oppose rotary oscillations of the housing. In such an arrangement, relative vibrations between the housing containing the light source and the detector means will not change the light flux from the light beams falling on the detector. Upon occurrence of vibrations, the light beams will rather be moved in parallel relative to the detectors, so as to be still focused in the focal point of the detector optical system. Making the aperture of the detector optical system large as compared with the beam cross section, ensures that, also during such vibrations, the whole beam will be received by the detector optical system.

The means for causing, in the case of thread break, the thread to move through the associated light beam preferably comprise an air outlet pipe also extending 5 across the pluralities of threads and a blower connected beam. I i

In order to make sure that all partial beams of the laser light beam have identical intensities, the transmittance of the first one of a total of rr partially transparent mirrors maybe l/n percent, the transmittance of the subsequent mirrors in the optical path being (n 2)/(n 1) 100%, (n 3)/=(n 2 100%... (n

K)/[n (K-1)] 100% if K is the current number of the mirror (2, 3 .n);

Preferably the evaluating circuit is adapted to discriminate between the following types of detector signals:

a. short time thread impulses, i

b. permanent signal upon failure of the laser or attenuation of the beam intensity c. long time interruption of the beams due to large objects, the warning signal being tripped by thread impulses.

An embodiment of the invention is described hereinbelow with reference to the accompanying drawings, in which:

FIG.1 shows schematically the structure and the optical path of a monitoring device according to the invention,

FIG.2 shows a preferred form of the device of FIG.1,

FIG.3 shows a modification of the embodiment of FIG.1,

FIG.4 shows an embodiment of the invention using a conventional light source and a geometric beam splitting,

FIG.5 is a perspective view illustrating the arrangement and path of the threads, and

FIG.6 is a side elevation of the structure shown in FIG. 5.

Reference numerals a to 10n designate groups of threads, i.e., threads extending at right angles to the plane of the paper of the drawing. Light beams 12a, 12b l2n are provided, with each beam monitoring a respective one of these groups of threads. Each of the beams falls on a photoelectric detector 14a, 14b l4n, respectively. Each photoelectric detector is located in the focal point of an associated imaging optical system 16a, 16b 16n.

A very small beam cross section is required for each of the light beams 12a to l2n. For this purpose, a single laser 18 is provided as light source. A laser beam 20 emanates from laser 18. In a tubular housing 22, mirrors 24a, 24b 24n are mounted parallel to each other and at an angle of 45 to the housing axis. The laser beam 20 falls on a first partially transparent mirror 24a at an angle of 45. There it is split up into two partial beams. One partial beam 12a is transmitted by mirror 24a, while a second partial beam 28 is reflected by the first mirror 24a. The reflected partial beam is directed along the housing axis and successfully impinges upon the partially transmitting mirrors 24b 24n, also at an angle of 45 A partial beam 12b l2n is reflected by each mirror 24b 24n, respectively, said partial beams being directed as monitoring light beams across the respective groups of threads 10b l0n and falling on the respective photoelectric detector 14b l4n.

The first partially transparent mirror 24a has a transmittance l/n 100 percent, n being the number of the partially transparent mirrors and of the required monitoring light beams 12a l2n. Mirror 24b has a transmittance of (n 2)/(n l) 100%. In general, the K" mirror has a transmittance of By this means, provision is made that all monitoring light beams 12a to l2n have identical intensities.

An air outlet pipe 30 having a plurality of air outlet nozzles extends across the pluralities to threads to be monitored. This air outlet pipe is parallel to the monitoring light beams 12a l2n and outside all these groups of threads. Each of the monitoring light beams is provided on the side of the respective group of threads remote from air outlet pipe 30. Air outlet pipe 30 is connected to a blower 32, whereby the plurality of threads are exposed to a uniform stream from one side. By appropriate dimensioning of the air outlet openings provision can be made that the pressure and the speed of the air flowing out is substantially constant over the whole length of the pipe. The air stream has no influence as long as all threads are intact. If, however, one of the threads in one of the groups of threads breaks, it will be blown towards the left in FIG. 1 and thereby will be moved through the associated monitoring light beam 12a or 12b or l2n, respectively. A short dark impulse is generated at the associated detector. The detectors 14a to 14n connected to an evaluating circuit which, preferably, is adapted to discriminate between short time thread impulses occurring when a broken thread is blown through the associated light beam, a permanent signal occurring, for example, in case of failure of the laser or of attenuation of the beam intensity, and a long time interruption of the light beam by relative large objects. A warning signal F is tripped by thread impulses.

The arrangement is also shown in FIGS. 5 and 6. As is conventional, the threads of each group are unreeled from a warp beam 15 and passed about a guide bar 17. The air in outlet pipe 30 is emitted through openings 30a toward the group of threads 10a. If a thread breaks the air blows the broken thread across the associated light beam 12a to momentarily break the light beam and produce a dark pulse at the detector 14a.

In the embodiment of FIG. 2 the tubular housing 22 consists of housing sections 220 22n which are connected with each other by means of threaded sleeves 36a 36nl. Each housing section comprises a partially transmitting mirror 24a to 24n, so that the desired number of monitoring light beams 12a l2n can be provided by simply combining the appropriate number of housing sections.

The embodiment of FIG. 3 is similar to that shown in FIGS. 1 and 2, corresponding elements bearing identical reference numerals. The monitoring beams of light 10a 10n pass through the interior of pipes 38a 38m, the beams entering and leaving the pipes through windows (not shown) in the end faces of the pipes. The pipes are provided with axial slots 40a 40n and connected to a suction source 42 through a suction pipe 44. If a thread breaks, it will be drawn by the suction into the axial slot of the respective pipe and interrupts the monitoring light beam.

In the embodiment of FIG. 4, which is similar in structure to that of FIG. 1, a conventional light source 46 such as an incandescent lamp filament is used. A collimated light beam is formed from this light source by means of a collimator lens 48. Fully reflective beam splitting mirrors 52a 5211 are impinged upon by different partial beams of this collimated light beam and direct these partial beams as monitoring light beams 12a l2n through windows 54a 54n, said windows being in the form of positive lenses.

I claim:

1. A photoelectric monitoring device for groups of threads, such as in warp knitting machines, in which monitoring beams of light are directed transversely across one group of threads each and impinge on photoelectric detectors, the improvement comprising that the monitoring beams of light are formed by providing a single light source forming a light beam and by arranging a plurality of beam splitting mirrors one behind the other in the optical path of said light beam and at an angle to the beam axis thereof.

2. A photoelectric monitoring device as claimed in claim 1 wherein said light source is a laser.

3. A photoelectric monitoring device as claimed in claim 1, wherein said beam splitting mirrors are partially transparent mirrors.

4. A photoelectric monitoring device as claimed in claim 1, wherein said light source is a laser emitting a laser beam, and a first partially transparent beam splitting mirror is located in the optical path of said laser beam at an angle to the beam axis, the partial beam transmitted by said first partially transparent mirror being directed across a first group of threads to a photoelectric detector as a first monitoring light beam, and wherein a plurality of additional partially transparent mirrors are located in the optical path of the partial beam reflected by said first partially transparent mirror at an angle to the beam axis, the partial beams reflected by said additional partially transparent mirrors being directed across additional pluralities of threads to one photoelectric detector each as additional beams for the monitoring of the threads.

5. A photoelectric monitoring device as claimed in claim 4 wherein said first and additional partially transparent mirrors are arranged parallel to each other and at an angle of 45 to the beam axis.

6. A photoelectric monitoring device as claimed in claim 4, wherein the partially transparent mirrors are mounted in a tubular housing having windows in its wall for the light beams.

7. A photoelectric monitoring device as claimed in claim 1 and further comprising: a detector optical system in the optical path of each said monitoring light beams, the detector for the respective monitoring light beam being located in the focal point of said detector optical system, the aperture of said detector optical system being large as compared to the monitoring light beam cross section.

8. A photoelectric monitoring device as claimed in claim 7, wherein said light source is a laser emitting a laser beam and said laser and said beam splitting mirrors are mounted in a housing, the housing being supported by vibration damping means, said vibration damping means being designed, however, to oppose rotary oscillations of the housing.

9. A photoelectric monitoring device as claimed in claim 1, wherein an air outlet pipe extends across said groups of threads and a blower is connected to said air outlet pipe, each of said light beams being formed on the side of the respective group of threads remote from said outlet pipe.

10. A photoelectric monitoring device as claimed in claim 6 wherein the tubular housing comprises a plurality of tubular housing sections, the housing sections being connected by threaded sleeves.

11. A photoelectric monitoring device as claimed in claim 1, wherein each of the monitoring light beams passes through a pipe extending across one of the pluralities of threads and provided with an axial slot, said pipe being connected to a suction source.

12. A photoelectric monitoring device as claimed in claim 1, wherein said beam splitting mirrors are fully reflecting mirrors located in different partial cross sec tions of the light beam emanating from said light source to thereby fully reflect the intercepted part of the beam and permit the remaining, unintercepted part, to pass by.

13. A photoelectric monitoring device as claimed in claim 4, wherein the transmittance of the first of a total of n partially transparent mirrors is l/n percent and the transmittance of the successive mirrors in the optical path is v (n 2)/(n 1) 100%, (n 3)I(n 2) 100% (n K being the current number of the mirror.

14. In a photoelectric monitoring device for use with a knitting machine or the like having n groups of threads to be monitored against breakage of a thread, wherein said device includes means to produce n beams of light, one for each group respectively, and a photoelectric detector for each beam respectively to produce a signal when the respective beam is inter cepted by a broken thread, the improvement comprismg:

said means comprising a laser for producing a single main beam of light having a relatively small cross section, n mirror means positioned transverse to said main beam, each mirror means being for a respective group, said mirror means being arranged in a series such that each of the mirror means except that last permits part of the main beam to pass by while forming from the main beam a partial beam to monitor the respective group.

15. In a device as set forth in claim 14, wherein the first mirror means in said series has a transmittance of approximately l/n 100 percent and the transmittance of the successive mirrors in the series is approximately (n 2)/(n l) 100%, (n 3)/(n 2) 100% (n K)/[n (K-1)] 100% K being the current number of the mirror.

T UNITED STATES PATENT oTTTcE CERTIFICATE 9F C ECTION Patent No. 3,760,184 Dated September 18, 1973 Inventor(s) Peter Brose It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 3, line 23 "successfully" should be "successively" Col. 6, line 31 "that last" should be "the last" Signed and sealed this 16th day or April 1971;.

(SEAL) Attest;

EDWARI.) ["I-FLETGHJER,JR 0.. MARSHALL'DANN Attesting Officer Commissioner of Patents FORM PC3-1050 uscoMM-Dc 60376-P69 W U.S. GOVERNMENT PRINTlNG OFFICE: I969 36 6"33, 

1. A photoelectric monitoring device for groups of threads, such as in warp knitting machines, in which monitoring beams of light are directed transversely across one group of threads each and impinge on photoelectric detectors, the improvement comprising that the monitoring beams of light are formed by providing a single light source forming a light beam and by arranging a plurality of beam splitting mirrors one behind the other in the optical path of said light beam and at an angle to the beam axis thereof.
 2. A photoelectric monitoring device as claimed in claim 1 wherein said light source is a laser.
 3. A photoelectric monitoring device as claimed in claim 1, wherein said beam splitting mirrors are partially transparent mirrors.
 4. A photoelectric monitoring device as claimed in claim 1, wherein said light source is a laser emitting a laser beam, and a first partially transparent beam splitting mirror is located in the optical path of said laser beam at an angle to the beam axis, the partial beam transmitted by said first partially transparent mirror being directed across a first group of threads to a photoelectric detector as a first monitoring light beam, and wherein a plurality of additional partially transparent mirrors are located in the optical path of the partial beam reflected by said first partially transparent mirror at an angle to the beam axis, the partial beams reflected by said additional partially transparent mirrors being directed across additional pluralities of threads to one photoelectric detector each as additional beams for the monitoring of the threads.
 5. A photoelectric monitoring device as claimed in claim 4 wherein said first and additional partially transparent mirrors are arranged parallel to each other and at an angle of 45* to the beam axis.
 6. A photoelectric monitoring device as claimed in claim 4, wherein the partially Transparent mirrors are mounted in a tubular housing having windows in its wall for the light beams.
 7. A photoelectric monitoring device as claimed in claim 1 and further comprising: a detector optical system in the optical path of each said monitoring light beams, the detector for the respective monitoring light beam being located in the focal point of said detector optical system, the aperture of said detector optical system being large as compared to the monitoring light beam cross section.
 8. A photoelectric monitoring device as claimed in claim 7, wherein said light source is a laser emitting a laser beam and said laser and said beam splitting mirrors are mounted in a housing, the housing being supported by vibration damping means, said vibration damping means being designed, however, to oppose rotary oscillations of the housing.
 9. A photoelectric monitoring device as claimed in claim 1, wherein an air outlet pipe extends across said groups of threads and a blower is connected to said air outlet pipe, each of said light beams being formed on the side of the respective group of threads remote from said outlet pipe.
 10. A photoelectric monitoring device as claimed in claim 6 wherein the tubular housing comprises a plurality of tubular housing sections, the housing sections being connected by threaded sleeves.
 11. A photoelectric monitoring device as claimed in claim 1, wherein each of the monitoring light beams passes through a pipe extending across one of the pluralities of threads and provided with an axial slot, said pipe being connected to a suction source.
 12. A photoelectric monitoring device as claimed in claim 1, wherein said beam splitting mirrors are fully reflecting mirrors located in different partial cross sections of the light beam emanating from said light source to thereby fully reflect the intercepted part of the beam and permit the remaining, unintercepted part, to pass by.
 13. A photoelectric monitoring device as claimed in claim 4, wherein the transmittance of the first of a total of n partially transparent mirrors is 1/n 100 percent and the transmittance of the successive mirrors in the optical path is (n - 2)/(n - 1) 100%, (n - 3)/(n - 2) 100% . . . (n - K)/(n -(K-1)) 100%, K being the current number of the mirror.
 14. In a photoelectric monitoring device for use with a knitting machine or the like having n groups of threads to be monitored against breakage of a thread, wherein said device includes means to produce n beams of light, one for each group respectively, and a photoelectric detector for each beam respectively to produce a signal when the respective beam is intercepted by a broken thread, the improvement comprising: said means comprising a laser for producing a single main beam of light having a relatively small cross section, n mirror means positioned transverse to said main beam, each mirror means being for a respective group, said mirror means being arranged in a series such that each of the mirror means except that last permits part of the main beam to pass by while forming from the main beam a partial beam to monitor the respective group.
 15. In a device as set forth in claim 14, wherein the first mirror means in said series has a transmittance of approximately 1/n 100 percent and the transmittance of the successive mirrors in the series is approximately (n - 2)/(n - 1) 100%, (n - 3)/(n - 2) 100% . . . (n - K)/(n -(K-1)) 100% K being the current number of the mirror. 